TRAFFIC COLLISION AVOIDANCE SYSTEMTCAS

Augustine k JoseKarunya university

What is TCAS

TCAS, and pronounced tee-kas) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft.  International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg .

Structure

OPERATION

It uses transponder mode c and mode s.  Interrogates 1030 MHZ Receives reply via 1090 MHZ. This interrogation-and-response cycle may occur several times per

second. The TCAS builds a 3d map of airspace near aircraft , incorporating their range (garnered from the interrogation and response

round trip time), altitude (as reported by the interrogated aircraft), and bearing (by the directional antenna from the response).

2 types of alerts:

TA which is a threat advisory that alerts the pilot that another aircraft is close enough to be a potential threat

RA is a resolution advisory that means the other aircraft IS a threat (30 seconds to a possible collision) and issues commands to evade a collision.

7 TCAS Basics

TCAS I - Aircraft with 10 to 30 seats Traffic Advisory Only

TCAS II - Aircraft with more than 30 passenger Traffic Advisory Resolution Advisory

Mode S – Detailed flight parameter information ATC Ground Based Radars Other Mode S equipped aircraft

Provides coordinated RAs

8 Traffic Advisory

A TA indicates that an aircraft is a potential threat RA may be necessary w/in, approx, the next 25 sec most commonly displayed as a yellow circle

9 Resolution Advisory

An RA indicates that an aircraft Is a threat displayed as a red square accompanied by a recommended vertical maneuver.

TCAS on a Radar Display

Textbook page 148

TCAS on Vertical Speed Indicator

TCAS on Vertical Speed Indicator

The red arc indicates the area to avoid, the pilot always shoots for the green arc.

In this example, the airplane is descending at about 3000 feet per minute.

Textbook page 149

TCAS on an EFIS screen

Textbook page 149

14 AFI 11-202 Vol 3 Response to TCAS Alerts.

If a TCAS RA requires maneuvering contrary to ATC instructions, right-of-way rules, cloud clearance requirements, or other VFR/IFR flight rules, pilots are expected to follow the TCAS RA.

15 Ten Fundamental Dos and Don’ts1. TCAS must be operated in RA mode to provide full safety benefit2. Pilots must follow all RAs promptly and accurately3. Pilots must never maneuver in the opposite sense of an RA4. Pilots must report RAs to controllers as soon as possible5. Controllers must not interfere with pilots’ reactions to RAs6. Vertical speed must be reduced in response to “Adjust Vert Spd” 7. TCAS traffic displays must not be used for self-separation8. Vertical speed must be reduced when approaching cleared FL9. VFR pilots must operate their altitude reporting transponder10. Pilots and controllers must be recurrently trained on TCAS ops